I was just wondering if there was any difference between the two in relation to prizes given out and stuff, and whether or not one is better than the other!

I'm not sure...I know you can get an achievement for their quests which is actually 2 separate achievements for each one of them, so that is one difference

I've noticed that usually Nori asks for more pink and lighter colored items, and Mori asks for more purple and darker colored items. If I'm not mistaken the item prizes they give are like that too. Neither one is better than the other but like mentioned, there are 2 separate quest achievements for them.